Presplitting blasting assembly



y 25, 1967 w. L. K. SCHWOYER ETAL 3,332,349

PRESFLITTING BLASTING ASSEMBLY Filed Aug. 16, 1965 United States Patent 3,332,349 PRESPLITTING BLASTING ASSEMBLY William L. K. Schwoyer, Allentown, and Thomas P. Bowling, Fullerton, Pa., assignors to Trojan Powder Company, Allentown, Pa., a corporation of New York Filed Aug. 16, 1965, Ser. No. 479,708 13 Claims. (Cl. 102-24) This invention relates to an improvement in the blasting technique known as presplitting, and, more particularly, to a blasting assembly especially adapted for use in presplitting blasting.

Presplitting is a system of blasting whereby a shear plane or break line is established in a rock formation to be blasted. This break line prevents over-break, and allows the blasting of a smooth face to a predetermined alignment. Because presplitting reduces vibration, blasting can often be carried out much closer to buildings, utilities, and other installations.

In normal presplitting practice, holes of from 1 /2 inches to 4 inches in diameter spaced 1 foot to 4 feet apart are drilled along the desired break line. The holes are loaded with explosives to achieve loading densities varying from 0.15 to 1.5 lbs. of explosives per foot of drill hole. To achieve the required density, cartridges of explosives are taped, tied or wired at specified intervals to a length of detonating fuse. Often the cartridges have to be cut into half or smaller increments in order to maintain the desired charging density. The completed lengths of detonating fuse with cartridges attached are lowered into the drill holes and the holes are stemmed with fine screening. The detonating fuse line in each hole is connected to a detonating fuse trunkline, and each hole is initiated simultaneously.

Although the foregoing system has received some commercial acceptance, it has many disadvantages both in efficiency and in safety. In order to achieve the desired loading density, it is necessary to fasten individual cartridges to the detonating fuse with tape, string or wire. This practice is rather cumbersome, and becomes quite expensive, due to the time required to make up the charges. The tape, string or wire are extra components, that must be purchased and stocked for the blasting oper ation. The explosives available are not always capable of producing the required loading density, and cartridges must be cut to reduce the size of individual charges. Cutting of the charges introduces the hazard of having to physically break down the explosive, plus the added hazards of requiring exposed explosives to be carried to and loaded in the drill hole. Wherever explosive cartridges are being cut, handled and carried, there always exists the possibility that loose explosives will be spilled around the work area.

In many instances, a central assembly area is set up, and a plurality of charges are fabricated, so that predetermined number of holes on be loaded. When this procedure is followed, there is, in addition to the hazards of exposed explosive cartridges and loose explosives in the work area, the hazards of having large quantities of explosives exposed on the ground.

The explosives used for presplitting work are normally nitrogIycerine-sensitized, and can be ammonia gelatins, smei-gelatins or ammonia dynamites. These explosives are highly sensitive to shock and friction, and impart an added danger if they are removed from their original packing.

The nitrogIycerine-sensitized dynamites cause severe and persistent headaches, known as dynamite headaches. In presplitting work where personnel must cut the cartridges, fasten the cartridges to the detonating fuse, and carry the assemblies to the drill holes, they are constantly exposed to the nitrogIycerine explosives, and dynamite headaches are quite common.

The instant invention provides a presplitting blasting assembly which does away with the nuisance and expense of fastening individual cartridges to detonating fuse with tape, string or wire. The present invention also eliminates the need for and the hazard of physically breaking up explosive cartridges to reduce the size of individual charges, and the requirement of carrying exposed explosive to the drill hole and loading it therein. In addition, the explosive used in the present invention is a nitrostarch sensitized explosive and hence, will not cause dynamite headaches. Accordingly, the blasting assembly of the instant invention represents a significant advance and improvement over presently existing presplitting blasting assemblies.

The presplitting blasting assembly of the present invention, comprises, in combination, a train of two or more explosive cartridges containing a nitrostarch-sensitized explosive composition, disposed coaxially and held in an end-to-end relationship to one another by coupling means, with a detonating fuse retained against the cartridges by the coupling means.

The assembly of the invention is put together as follows. The fuse normally is run through the coupling means, and the loaded cartridges are then fitted end-to-end in the coupling means, with the detonating fuse held between the outer walls of the cartridges and inner walls of the coupling means. Thus, the coupling means holds the fuse in close proximity to or in contact with the outer walls of the cartridges to ensure the detonation of the cartridges. A column or train of explosive comprising a plurality of cartridges coupled in this way is thereby easily and quickly formed to any desired length and weight, and is characterized by strength and rigidity. Thus, the explosive can be lowered to position as a continuous column, or train, with complete assurance that none of the cartridges will drop from the column into the cavity, or stick in the drilled hole and prevent proper loading thereof, and that all will be detonated by the same fuse. The column can be coupled so that there is close contact between the ends of the cartridges of the column in the couplers, to facilitate propagation of the detonation down the column.

In using the presplitting blasting assembly of the instant invention, holes are drilled along a predetermined line in the ground area to be blasted. Presplitting blasting assemblies are lowered into the drilled holes, and the holes are stemmed with fi-ne screening. The detonating fuse of each blasting assembly is then connected to a common fuse, so that all the linked blasting assemblies can be detonated simultaneously.

The invention can be more readily understood by referring to the accompanying drawings, which represent preferred embodiments, and are not intended to limit the scope of the invention.

FIGURE 1 is a longitudinal view of a preferred embodiment of the presplitting blasting assembly of the invention.

FIGURE 2 is a perspective view of the assembly of FIGURE 1.

The presplitting blasting assembly shown in the figures comprises a plurality of cartridges, each of which is identified by the numeral 10, filled with a nitrostarchsensitized presplitting explosive 11. A plurality of coupling means or couplers, each of which is identified by the numeral 12, join said cartridges, so as to form a column or train of couplers and cartridges. A detonating fuse downline 14 of suitable material such as Primacord extends the length of the column, overlapping the ends thereof, and is held in place within the couplers against the external walls 15- of the cartridges to ensure the.

is run through the couplers 12 and 12' provided with grooves 13. The top end 16 of a first cartridge (indicated by dotted lines in FIGURE 1) is inserted in a first coupler 12 in a force-fit, such that the detonating fuse line is firmly held between the cartridge and the coupler 12. The butt end 18 of the cartridge 10 is then inserted in the same manner in a second coupler 12'. The top end 20 of a second cartridge 10' is then inserted in a lower portion of the second coupler 12 in close proximity to, if not touching, the butt end 18 of the first cartridge 10. The remaining cartridges of the column or train are then fitted together, top to butt, by means of the couplers, ina manner such that the detonating fuse line is run through the narrow space between the external walls of the cartridges and the couplers.

It is possible, by means of couplers, to connect the cartridges of the invention in trains of two or more; there is no upper limit on the number of cartridges in a train, inasmuch as this will depend upon the explosive shock required, the depth and diameter of the bore hole and of the cartridges, and the types of booster and explosive mixture employed.

Cartridges suitable for use herein can be any conventional cartridge of convenient length and diameter, proportionate to the amount of explosive needed for the explosive effect desired.

The cartridge containers can be formed of any container material. Convolute wound paper is inexpensive, and available in sufficient thickness of wall, and is therefore preferred. The cartridge can also be formed of plastic and cellulosic materials, such as polyethylene, ethyl cellulose, cellulose acetate, polypropylene, polytetrafluoroethylene, nylon, polyvinyl chloride, polystyrene and polyvinylidene chloride, and nonferrous metals, such as tin, copper and aluminum. Fibrous materials such as wood, paper, and cardboard can be used as such, or, if desired, can be impregnated with a synthetic resin to improve strength and water-resistance.

The explosive mixture employed in the presplitting blasting assembly of the invention is based on a nitrostarch-sensitized explosive mixture, containing ammonium nitrate as the principal inorganic nitrate, and optionally, nitrates of alkali and alkaline earth metals, such as sodium nitrate, potassium nitrate and barium nitrate, as a supplementary inorganic nitrate. In addition to the sensitizer and nitrates, optionally, one or more fuels can be used, including metal fuels and carbonaceous fuels.

The relative proportions of the various ingredients of this composition are important to the presplitting blasting operation. The nitrostarch sensitizer is employed in a proportion within the range of from about 6 to about weight percent, and the ammonium nitrate in a proportion within the range of from about 50 to about 75 weight percent.

Where a supplementary inorganic nitrate oxidizer is used, it is preferred to use sodium nitrate in the range of from 0 to about 10 weight percent.

The inorganic nitrates can be fine, coarse, or a blend of fine and coarse materials. Mill and prilled inorganic nitrates are quite satisfactory. For best results, the ammonium nitrate and the sodium nitrate should be finegrained.

The nitrostarch employed herein can be of any particle size. It can, for example, be fine, coarse, or a blend of fine and coarse material, a finely-divided impalpable powder being preferred.

In addition to these materials, as indicated hereinbefore, the explosive composition used in the instant blasting assembly may optionally include a metal fuel, for example, aluminum powder or flake aluminum. A metal fuel may comprise from 0 to about 25 weight percent of the composition. In addition to the metal fuel, a carbonaceous fuel can be included, as an optional ingredient, such as powdered coal, petroleum oil, coke dust, charcoal, bagasse, dextrin, starch, wood flour, bran, pecan meal, and similar nut shell meals. A carbonaceous fuel can be present in amounts of from 0 to about 40 weight percent. Mixtures of metal and carbonaceous fuels can be used, if desired.

carbonaceous fuels of low density also serve as bulking or density-reducing agents. Typical of such dual purpose fuels is bagasse.

An antacid, or other stabilizing materials, such as zinc oxide, calcium carbonate, aluminum oxide, and sodium carbonate, can also be added. Such ingredients can comprise from 0 to about 5 weight percent of the mixture.

An inert or porous material can be added to the instant explosive mixture in amounts of from 0 to about 10 weight percent of the mixture, to add bulk and reduce density. A preferred bulking agent is expanded vermiculite, which is an inert material. vermiculite is a hydrated magnesium aluminum iron silicate, containing approximately 38% SiO 21% MgO, 15% Al O 9% Fe O 5 to 7% K 0, 1% CaO, and 5 to 9% water. Also useful are the silica aerogels, which may be formed from silica, alumina, and other gel-forming metal oxides, silica flour and the hentones. Typical silica aerogels are those manufactured by Monsanto Chemical Company and marketed under the trade name, Santocel, such as Santocel C, Santocel A, Santocel AR, Santocel ARD, Santocel AX, Santocel CDV and Santocel CDVR. Other materials are fumed silica made by a combustion or vaporization process, and Linde silica flour, made by burning silicon tetrachloride and collecting the combustion products on cold plates analogous to the production of carbon black.

A preferred explosive composition suitable for use herein contains the following ingredients.

Sensitizer: Percent Nitrostarch 6.00-25.00 Oxidizer:

Ammonium nitrate 50.00-70.00 Sodium nitrate LOO-10.00 Fuels and bulking agents:

Bagasse 2.00-10.00 Sawdust LOO-10.00 Nut meal 1.005.00 Oat hulls 1.00-4.00 Vermiculite 1.00-10.00 Petroleum oil 0-4.00 Aluminum 1.50-3.00 Stabilizer:

Zinc oxide 0-5 .00

Total 100.00

Ingredients are varied as required to give the cartridge count necessary to produce loading densities of from 0.25 to 1.50 lbs. of explosive per foot of drill hole. Holes are normally drilled from about 6 to about 50 feet deep and from about 1 /2 to about 4 inches in diameter.

Any detonating fuse of conventional type is suitable for use herein. The fuse usually consists of a narrow tube filled with high explosive. When an explosion is initiated at one end of the fuse by means of a detonator, the explosive wave travels along the fuse with a high velocity, and causes the detonation of the cartridged high explosives to which it is held in close proximity by the couplers. By connecting the fuse to a fuse trunkline, and firing the fuse trunkline, for example, by by means of a blasting cap held snugly and firmly against the end of the fuse trunkline, each of the presplitting blasting assemblies of the invention can be exploded simultaneously. Exemplary detonating fuses which can be used herein include lead tubes filled with trinitrotoluene, aluminum block or tin tubes filled with picric acid, tubes of woven fabric filled with nitrocellulose or with pentaerythritol tetranitrate, and the like.

The coupling device employed in accordance with the invention can be any one of a number of conventional around its external surface and thus a corresponding series of raised portions around its internal surface. When a cartridge is inserted in the coupler, the gripping portions of the coupler abut and embrace the mating portions on the surface of the cartridge in a tight fit, thereby securing the cartridge to the coupler.

A typical presplitting blasting system comprises a plurality of cartridges filled with a nitrostarch-sensitized explosive having the following composition:

Percent by Weight Having regard to the foregoing disclosure, the following is claimed as the inventive and patentable embodiments thereof:

1. A presplitting blasting assembly comprising, in combination, a plurality of explosive cartridges, disposed in alignment end to end; a detonating fuse line; and a plurality of coupling means joining said cartridges end to end, one to another, and securing said fuse line against said cartridges, thereby forming a rigid, continuous explosive column, the detonating fuse line being threaded between the cartridges and the coupling means.

2. A presplitting blasting assembly comprising, in combination, a plurality of explosive cartridges, disposed in coaxial alignment, end to end with respect to one another; a detonating fuse line; and a plurality of coupling means joining said cartridges end to end, one to another, and securing said fuse line against said cartridges, thereby forming a rigid, continuous explosive column, the detonating fuse line being threaded between the cartridges and the coupling means.

3. A presplitting blasting assembly in accordance with claim 1 wherein said coupling means is comprised of a tubular member, and gripping means provided on said tubular member to engage and couple with said cartridges.

4. A presplitting blasting assembly in accordance with claim 1 wherein the cartridges contain a nitrostarchsensitized blasting explosive.

5. A presplitting blasting assembly in accordance with claim 4 wherein said explosive composition comprises from about 6 to about 25% by weight nitrostarch, and from about 50 to about 75% by weight of ammonium nitrate.

6. A presplitting blasting assembly in accordance with A claim 4 wherein said explosive composition comprises from about 6 to about 25 nitrostarch, from about 50 to about ammonium nitrate, and from about 1 to about 10% sodium nitrate.

7. A presplitting blasting assembly in accordance with claim 6 wherein said composition includes up to about 40% of a fuel.

8. A presplitting blasting assembly in accordance with claim 7 wherein said fuel comprises up to about 25% aluminum.

9. A presplitting blasting assembly in accordance with claim 7 wherein said fuel comprises a carbonaceous fuel.

10. A presplitting blasting assembly in accordance With claim 9 wherein said carbonaceous fuel comprises at least one fuel selected from the group consisting of bagasse, sawdust, nut meal, oat hulls, and petroleum oil.

11. A presplitting blasting assembly in accordance with claim 6 wherein said composition comprises from about 1 to about 10% vermiculite.

12. A presplitting blasting assembly in accordance with claim 6 wherein the explosive composition includes, in addition, up to about 5% of an antacid stabilizer.

13. A presplitting blasting assembly in accordance with claim 12 wherein said antacid stabilizer comprises zinc oxide.

References Cited UNITED STATES PATENTS 2,171,384 9/1939 Young 102-24 2,401,140 5/1946 Cordie 10224 2,577,110 12/1951 Cummings 149-56 X 3,083,127 3/1963 Griffith et a1. 149-59 BENJAMIN A. BORCHELT, Primwy Examiner. V. R. PENDEGRASS, Assistant Examiner. 

1. A PRESPLITTING BLASTING ASSEMBLY COMPRISING, IN COMBINATION, A PLURALITY OF EXPLOSIVE CARTRIDGES, DISPOSED IN ALIGNMENT END TO END; A DETONATING FUSE LINE; AND A PLURALITY OF COUPLING MEANS JOINING SAID CARTRIDGES END TO END, ONE TO ANOTHER, AND SECURING SAID FUSE LINE AGAINST SAID CARTRIDGES, THEREBY FORMING A RIGID, CONTINUOUS EXPLOSIVE COLUMN, THE DETONATING FUSE LINE BEING THREADED BETWEEN THE CARTRIDGES AND THE COUPLING MEANS. 